Gear ratio

thaipham25

I changed my sprockets to 60 teeth and 18 on the engine. I'm running 18" rear tires. The gearing ratio is 3.333 and i should be able to go about 72 mph. Since my rpm gauge is wrong, I'm guessing I'm running 4500 rpm.
I ran the hell out of my cart and i still can barely hit 51mph on a 1/2 mile strip. What am i doing wrong. Is my rpm wrong, am i not going over 3500rpm.
Vc460 with all the hook up

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BGW

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sho305

Max power should be in the 4K rpm area but ask Geoff to be sure, assuming no governor. Higher if it has a cam/etc mods on it. Do you have free flowing airbox and exhaust? If you have a gokart type setup and no cvt it will tend to make more power when you get to peak rpm around 4K, what ever speed you are at there. Stock engine will fall off around 4500 but don't know what package you have. They can rev higher than that with HD springs and timing key but still make less power up there so if geared high it might not want to go over that.

thaipham25

I have all the available upgrades in the package with intake exhaust flywheel 30" carb etc. Only thing i don't have is the 65lb valve springs. All valves are set perfectly. Maybe its my alignment. But nothing shakes too much.

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sho305

Check to see if the clutches are really hot after a run that might be a clue. It will scrub off energy if the alignment is off but you should be able to see if its that bad. Make sure it shifts all the way out. I changed the spring in mine it will not shift all the way now, have another spring to try in it (primary spring).

thaipham25

Clutch isn't hot and my cart is probably 200lbs total weight. I'm 165lb so me and cart is 365lb. Idk if weight has a lot ti do with it but i dont think that's too heavy for a cart right?

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sunking

Not enough torque to go any faster.

thaipham25

:(

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sho305

You have to know the power peak rpm, you have to have the engine shift there to get top speed and gear it so it does not run out of gearing before that (and make rpm go higher and lose power).

thaipham25

My new tach just arrived and i got it running close to 5000rpm. what's weird is that my max speed is at 49mph now where i was running 52mph before the tach.

Streetbu

Just because the theoretical top speed is 72 mph doesn't mean you'll go that fast. It also has to do with hp, torque, wind resistance, friction (tire resistance), etc. Using tire diameters, gear ratio and rpm gives you that mph figure, but that would be with ZERO resistance. You have A LOT of aerodynamic issues as does anything, friction to the ground, power loss thru the drivetrain etc. 50-ish mph sounds very reasonable.